For Phytochemical marker isolation /qualification and quantification HPTLC has many added advantages over HPLC because

1.You can segregarte crude mixture of phyto extracts (HPLC needs some purication to avaoide some higher mol.wt compounds and gums/resins.

2.HPTLC  separation of compounds is more precise and accurate if you use automatic spotter and scanner and develop in  right TLC chambers with appropiate solvent mixture ( TLC accurate separation is by  principles of partition chromatography ) 

3.Added advantage of HPTLC is if the phytocompounds are non fluorescent nor detectable at particular lambda max you can use an appropiate spary reagent  for detection and quantification.

4.HPTLC is more economical when you use very small plates for standerdisation before real quantifiaction. (You may refer many research articles on HPTLC when we have published not only HPTLC for phytochemicals but also quantified many markers in plasma   BE/BA clical sudies(

HPLC will be more convenient for quantitation of a natural drug from unknown plant samples than HPTLC. But you need standards for quantification. 

For Phytochemical marker isolation /qualification and quantification HPTLC has many added advantages over HPLC because

1.You can segregarte crude mixture of phyto extracts (HPLC needs some purication to avaoide some higher mol.wt compounds and gums/resins.

2.HPTLC  separation of compounds is more precise and accurate if you use automatic spotter and scanner and develop in  right TLC chambers with appropiate solvent mixture ( TLC accurate separation is by  principles of partition chromatography ) 

3.Added advantage of HPTLC is if the phytocompounds are non fluorescent nor detectable at particular lambda max you can use an appropiate spary reagent  for detection and quantification.

4.HPTLC is more economical when you use very small plates for standerdisation before real quantifiaction. (You may refer many research articles on HPTLC when we have published not only HPTLC for phytochemicals but also quantified many markers in plasma   BE/BA clical sudies(

From a technical point of view, you must at least know the specificity, the linearity and the repeatability of the analytical method whatever the technology you use. That means there is no co-elution, the response is proportional to the amount of your product and it gives the same results when performed several times. This depends on the level of accuracy you need (have a look on ICH Q2(R1) guideline)

HPTLC has many advantages : economical, simple to use, run in parallele, large choice of reagents. But if you need a good reproducibility in quantitation, a plotter and scanner is definitely needed as mentionned by B.k Chakravarthy.

The advantage of HPLC is the large choice of solid phases and the high number of plates. If you encountered difficulties with HPTLC on pure silica (tailing, co-elution), you can try reverse phase HPTLC but it is more expensive and the number of reagents becomes more limited. HPLC may be more interesting. A good washing of the column between the runs or a preparation of the samples may be needed to remove the resin. If your samples come from different plants, the risk of co-elution is higher. So HPLC seems to be more suitable than HPTLC.

On a regulatory point of view, the HPTLC will not be accepted. If you want to use your results to fill a regulatory dossier, the HPLC will be requested along with the analytical validation data.

The question  pertains to phytochemical drugs and no phyto lab is complete with out TLC technology usage. HPTLC technologies with plotter and scanner facility are the most appropriate TLC technique for conformity with GMPs and are well accepted regulatory tools for more precision and accuracy .

TLC characterizations are among the key identity tests in most pharmacopoeial monographs . TLC Pharmacopoeial standards are typically used by industry as a basis for meeting QC requirements and current good manufacturing practices (cGMPs). TLC is a relatively low-cost, highly versatile tool for developing specifications for raw materials, as well as for the various preparations for which pharmacopoeial standards are created. HPTLC is used by the many herbal pharmacopoeia like Indian herbal pharmacopoeia (IHP) /American Herbal Pharmacopoeia (AHP) in the development of monograph identity standards, the identification of adulterating species, and the development of AHP-verified BRMs. HPTLC is a valuable tool for screening plant samples that pharmacopoeias must review in the development of monographs and botanical reference materials (BRMs).

HPLC since introduced much before HPTLC has wider acceptability,however,in phyto chemistry the disadvantage of HPLC is  suitability selection of columns for better resolution and subsequent column cleaning procedures for each sample.

Eventhough these deconvolution techniques complement each other, It is important to understand the limitations of each technique in relation to the objective.  If quantitation is the prime objective, the preference will be for HPLC.  I agree with Alain Chenede's points.  HPTLC is a semi-quantitative and open-ended  technique as not all  the absorption/reflectance from the compound is captured by the detector, there by making the assay accuracy to be in a very narrow range(due to lineary issues).  With hplc being a closed system , the absorption/reflectance due to eluting compounds is complete (without any loss) making the quantitation lot of more accurate.

I do not agree with the  last point made by Dr.Chakravarty on suitability of HPTLC in Phytochemistry. Most HPTLC applications tend to use normal phase silica only with the choices of other phases limited by the cost of HPTLC plates (eg. RP18 or RP8 plates). Again,If one looks at any pharmacopoeial or other compendial methods for medicinal herb constituents assay, the regulators all over the world  insist on HPLC method of quantitation. 

While HPTLC is a good qualitative technique, mostly used for identification of  extracts/species by finger-prints (based on the reasons provided by Dr.Chakravarti), HPLC is the most preferred quantitative tool available in phytochemical analysis. 

 In one phrase :

HPTLC is the method of choice to know what u have in ur crude extract but HPLC is used to quantify what already known.

1. 1. The discussion pertains to quantitation of phytocompounds by HPTL vs HPLC while comparing with an unknown plant / herb……it is suggested to the researcher for easy and cost effective experiments within available lab/ finance resources to focus on HPTLC experiments with automated plotter and scanner in closed chamber, rather on more costly and more time consuming HPLC method. Both methods have advantages and disadvantages as for the phyto compounds are concerned (pl. check up IFC details)

o 2.It is not true to say that HPTLC is not acceptable to many regulators for quantification and they insists only on HPLC method . They accept any validated methods which are a part of Pharmacopoeia standards for the product . Many documented reports are available on comparative validation and advantages of HPTLC on the reliability , analytical performance , including linearity, range, precision, accuracy, detection , quantization limits and were statistically validated and accepted as a part of official compendiums especially for herbals and dietary supplements (USPGeneral Chapters: CHROMATOGRAPHY - first page www.pharmacopeia.cn/v29240/usp29nf24s0_c621_viewall.html. J AOAC Int. 2010 Sep-Oct;93(5):1349-54. Élan M. Sudberg July 24, 2014: ) Of course one need to be accurate and precise in doing the experiment for reproducibility.

Dear all, it is now quite evident from your suggestions that HPTLC is effective as qualitative tool and will be used as quantitative technique if supported with data on precision, accuracy and reproducibility. HPLC is still method of choice over HPTLC for quantitation.